1. Technical Field
The present invention relates to a boost converter for boosting an input voltage thereof.
2. Related Art
An existing chopper boost circuit, as disclosed in U.S. Pat. No. 7,804,281, includes a switching element (N channel MOSFET), a pair of inductors, and a diode, to boost an input voltage to output a boosted voltage. More specifically, the pair of inductors are electrically connected to the respective terminals of the switching element, and an anode of the diode is electrically connected to the junction between one of the inductors and the switching element.
In such a chopper boost circuit, floating capacitors may be formed between the boost circuit and a casing (frame ground). More specifically, for example, floating capacitors may be formed between the drain of the switching element and the casing and between the cathode of the diode and the casing. In the presence of such floating capacitors, a variation in voltage applied across the switching element may cause a common-mode current to flow to the casing. More specifically, the floating capacitors between the boost circuit and the casing are charged and discharged through the variation in applied voltage across the switching element, which will cause the common-mode current to flow to the casing. The common-mode current flowing to the outside via the casing may, for example, lead to interference with some other electronic devices.
To address such deficiencies, the boost circuit disclosed in U.S. Pat. No. 7,804,281 requires a predefined balanced condition between the inductance values of the pair of inductors and the capacitance values of the pair of floating capacitors between the boost circuit and the casing. More specifically, for example, it is required that the inductance values of the pair of inductors coincide with each other and the capacitance values of the pair of floating capacitors coincide with each other. This may lead to reduction of common-mode current.
With the technique disclosed in U.S. Pat. No. 7,804,281, the common-mode current can be reduced. In some situations, however, where the boost circuits are designed for mass production, it may be difficult to satisfy the aforementioned balanced conditions between the inductance values of the pair of inductors and the capacitance values of the pair of floating capacitors. When the balanced conditions are not satisfied, sufficient reduction of the common-mode current may not be expected.
In consideration of the foregoing, it would therefore be desirable to have a boost converter capable of substantially reducing a common-mode current flowing to the outside of a boost circuit.